A variety of valves are used to control flow of actuating fluids in many well applications and other flow control applications. For example, valves are employed in wellbore drilling applications to control the actuation of tools located in the wellbore being drilled. During wellbore drilling operations, valves positioned in a drilling assembly can be selectively actuated to control the direction of drilling. The valves may be positioned, for example, to control the flow of drilling mud to actuating pads which are extended and contracted in a controlled manner to steer the drill bit and thereby drill the wellbore in a desired direction.
In some drilling applications, rotary steerable systems are employed to control the direction of drilling during formation of the wellbore. A rotary steerable system may utilize a drill bit coupled with a drill collar and rotated to drill through the rock formation. A plurality of steering pads is selectively actuated in a lateral direction to control the direction of drilling, and the steering pads may be controlled by a variety of valves and control systems. In some applications, rotary valves are held at desired angular orientations with respect to the rotating drill collar to control flow of drilling mud to the steering pads. A rotary valve may be held in a geostationary position by a control cartridge in, for example, a strap-down system. However, existing systems are limited with respect to accurately controlling the direction of drilling, providing options for changing the direction of drilling, and performing additional functions while drilling. Existing strap-down systems use a motor to orientate a valve opening but provide no advanced control. The motor either keeps the valve geostationary or allows it to rotate slowly.